;
var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";  
var base64DecodeChars = new Array(-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);  
/** 
 * base64编码 
 * @param {Object} str 
 */  
function base64encode(str){  
    var out, i, len;  
    var c1, c2, c3;  
    len = str.length;  
    i = 0;  
    out = "";  
    while (i < len) {  
        c1 = str.charCodeAt(i++) & 0xff;  
        if (i == len) {  
            out += base64EncodeChars.charAt(c1 >> 2);  
            out += base64EncodeChars.charAt((c1 & 0x3) << 4);  
            out += "==";  
            break;  
        }  
        c2 = str.charCodeAt(i++);  
        if (i == len) {  
            out += base64EncodeChars.charAt(c1 >> 2);  
            out += base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));  
            out += base64EncodeChars.charAt((c2 & 0xF) << 2);  
            out += "=";  
            break;  
        }  
        c3 = str.charCodeAt(i++);  
        out += base64EncodeChars.charAt(c1 >> 2);  
        out += base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));  
        out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));  
        out += base64EncodeChars.charAt(c3 & 0x3F);  
    }  
    return out;  
}  
/** 
 * base64解码 
 * @param {Object} str 
 */  
function base64decode(str){  
	return utf8to16(decode(str));
}
//真正的解码方法
function decode(str){
	var c1, c2, c3, c4;  
    var i, len, out;  
    len = str.length;  
    i = 0;  
    out = "";  
    while (i < len) {  
        /* c1 */  
        do {  
            c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];  
        }  
        while (i < len && c1 == -1);  
        if (c1 == -1)   
            break;  
        /* c2 */  
        do {  
            c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];  
        }  
        while (i < len && c2 == -1);  
        if (c2 == -1)   
            break;  
        out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));  
        /* c3 */  
        do {  
            c3 = str.charCodeAt(i++) & 0xff;  
            if (c3 == 61)   
                return out;  
            c3 = base64DecodeChars[c3];  
        }  
        while (i < len && c3 == -1);  
        if (c3 == -1)   
            break;  
        out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));  
        /* c4 */  
        do {  
            c4 = str.charCodeAt(i++) & 0xff;  
            if (c4 == 61)   
                return out;  
            c4 = base64DecodeChars[c4];  
        }  
        while (i < len && c4 == -1);  
        if (c4 == -1)   
            break;  
        out += String.fromCharCode(((c3 & 0x03) << 6) | c4);  
    }  
    return out; 
}
/** 
 * utf16转utf8 
 * @param {Object} str 
 */  
function utf16to8(str){  
    var out, i, len, c;  
    out = "";  
    len = str.length;  
    for (i = 0; i < len; i++) {  
        c = str.charCodeAt(i);  
        if ((c >= 0x0001) && (c <= 0x007F)) {  
            out += str.charAt(i);  
        }  
        else   
            if (c > 0x07FF) {  
                out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));  
                out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));  
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));  
            }  
            else {  
                out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));  
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));  
            }  
    }  
    return out;  
}  
/** 
 * utf8转utf16 
 * @param {Object} str 
 */  
function utf8to16(str){  
    var out, i, len, c;  
    var char2, char3;  
    out = "";  
    len = str.length;  
    i = 0;  
    while (i < len) {  
        c = str.charCodeAt(i++);  
        switch (c >> 4) {  
            case 0:  
            case 1:  
            case 2:  
            case 3:  
            case 4:  
            case 5:  
            case 6:  
            case 7:  
                // 0xxxxxxx  
                out += str.charAt(i - 1);  
                break;  
            case 12:  
            case 13:  
                // 110x xxxx 10xx xxxx  
                char2 = str.charCodeAt(i++);  
                out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));  
                break;  
            case 14:  
                // 1110 xxxx10xx xxxx10xx xxxx  
                char2 = str.charCodeAt(i++);  
                char3 = str.charCodeAt(i++);  
                out += String.fromCharCode(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0));  
                break;  
        }  
    }  
    return out;  
}  
